1. Field of the Invention
This invention relates to pumps and motors and more particularly to a rotating engine having a reciprocating piston received between guide members in a casing or cylinder.
2. Prior Art
Displaced piston engines of the type to which this invention relates comprise a rotor rotating in a cylindrical casing or cylinder. The working chamber is defined by guide surfaces on the rotor, the inside wall of the casing, and the end faces of a displaceable double ended piston received between the guide surfaces and which is actuated by or displaces a working medium within the working chambers at right angles to the axis of rotation.
Machines of this type are described, for example, in German Pat. No. 640,937 and in the German Offenlegungsschrift No. 1,451,742. In machines of the type described in those references, the displacement movement of the double acting piston is transmitted without a connecting rod by a crank which is connected to the shaft, in one instance, by an eccentric mount and in the other instance, by a central mount. In those instances where an eccentric shaft is used, the crank is attached to a bearing pin which is seated in the piston. In the case of central shaft mounting machines, it is necessary to provide a slide block which can be shifted cross-wise or transversely of the piston to provide a seat for the crank-pin bearing.
It is an object of the present invention to transform the displacement movement of the piston into a rotary movement directly without the use of a crank in the case of a central shaft support and with the added possibility of varying the piston stroke as required and the further possibility of providing a plurality of pistons in a star arrangement.
To this end, according to the present invention, the guide surfaces which are part of the rotor and which limit the working chamber are provided as surfaces of two separate guide members. Further, the contacting surfaces of the guide members and of the piston are arcuately curved coaxially in such a manner that the guide members are coupled together in their oscillatory movement in the casing in dependent relation to the piston stroke. One of the guide members is firmly attached to the shaft for rotation therewith or to an intermediate part which is itself firmly attached to the shaft for rotation therewith.
In such a construction, the displacement movement of the piston causes the guide members to move about the axis of rotation as a result of a cam thrust exerted on them by movement of the piston. This movement about the axis of rotation can then be transmited directly to the shaft because one of the guide members is connected to the shaft. The coupling of the guide members effectively limits the stroke of the piston, which operates, in effect, as a free piston. This being the case, there is a wedge effect to some extent which insures the maintenance of an effective seal between the piston and the guide members.
The curvature of the two piston surfaces and the guide members is important, however, they may be curved convexly or concavely so long as the curvature is one of equal radii. However, it is kinematically more effective if the piston surfaces are curved convexly and the guide surfaces of the guide members are curved correspondingly concave. In such a case, the guide members have a sickle-shape in the basic embodiment when only one displaceable piston is disposed in the rotor.
The coupling together of the two guide members may be accomplished in numerous ways. Primarily, this invention teaches guide members which engage a control ring which is mounted eccentrically of the axis of rotation and which is able to rotate. The guide members and the control ring engage one another via a plate-shaped intermediate element which is mounted for rotary oscillation in the guide member or in the control ring, the intermediate elements being radially or substantially radially slidable in one of the two.
According to the present invention, three types of arrangements are provided for the control ring. In the first, the control ring is mounted at the periphery of the machine having a rotating casing, and one of the guide members is connected rigidly to the casing while the other is slidable on the casing, an opening in th casing allowing oscillatory movement of the intermediate member which is provided between the control ring and the guide member slidable on the casing.
In the second arrangement, the control ring is mounted laterally, one of the guide members is disposed rigidly on the rotating casing and one intermediate element is disposed rigidly thereon while the other guide member is disposed rigidly on one rotating end wall and the intermediate element associated therewith is disposed rigidly thereon. The first intermediate element is slidably guided at its free end on the shaft which is connected to the end wall so as to rotate therewith, while the free end of the second intermediate element is guided slidably on the laterally projecting casing.
The third solution provides a very compact construction with a stationary casing and stationary end walls. The control ring is disposed inside a hollow piston, which is formed with apertures for the intermediate elements and for a hollow journalling of the control ring. One of the intermediate elements forms a rotationally rigid connection between one guide member and the shaft which passes through the piston and which also forms the control ring.
In all three cases, in the development of the invention, the sickle-shaped chamber or chambers defined by the control ring and central machine parts, such as the casing, shaft, and housing ring, serve as additional working chambers in which the intermediate elements rotate as power members.
Such devices are versatile, for example, an arrangement according to the third embodiment may be used as a coolant or lubricant pump, while the first two embodiments lead to a combination of rotary displaced piston and rotary valve piston engines.
In an important improvement, the control ring bearing is made adjustable so as to allow adjustment of the control ring eccentricity which in turn controls the piston stroke. In this way it is possible to use such devices as a fluid clutch or brake.
Additionally, the gude members can be coupled together by a transmission comprising elliptical or eccentric spur gears or by an anti-parallel crank drive and a countershaft.
Where the machine is constructed as a twin or tandem machine comprising two pistons, one piston is utilized to carry out the first and second stroke while the other piston carries out the third and fourth stroke in the four stroke machine. While such a division is known in other machines, it has not been used in the case of a rotary piston machine operating practically with free pistons.
In comparison with previously known machines, it is now possible to dispose a plurality of displaced pistons in the rotor in the form of a star. In this case the guide members have a symmetrical shape in keeping with the previously discussed embodiment and each of them is associated with two displaceable pistons. The guide members are then alternately disposed free and rigidly connected to a rotating housing part, i.e., the rotating casing, in the direction of rotation and the movement of the pistons is controlled by an elliptical or eccentric cam shaft.
In another modification, in the direction or rotation, the guide members are alternately connected to a rotating housing part so as to rotate therewith and to the shaft so as to rotate therewith, and one group of guide members is connected to the other group in the manner described hereinbefore, i.e., by a control ring or a transmission.
There is a further possiblity of obtaining additional working chambers in the case of a rotating casing by providing, across the circumference or in each part of the periphery of the casing which is continuously covered by a guide member not connected to the casing, any abrupt enlarged radius in comparison with the cylindrical member. The resulting curved chamber can form the working space of a plate shaped radial power member rigidly connected to the guide member. This power member can then perform the same oscillating movement as the guide part.
In dimensioning the radius of curvature of the contact surfaces between the piston and guide members, attention must be paid to the geometry of movement of the pistons and guide members and also to the fact that the piston surfaces act as thrust cams. As a rule of thumb, it may be stated that the radius of curvature in the case of a singlely divided cylindrical member should be at least equal to the casing diameter, while in the case of a multi-divided cylindrical member, i.e., the star arrangement of this invention, it should be at least equal to the casing radius. In the first case, a ratio of 1:1 to 3:2 between the radius of curvature of the contact surfaces and the casing diameter and in the second instance, a ratio of 2:1 between the radius of curvature in the casing radius has proven to be advantageous, since it permits a relatively large piston stroke while retaining sufficient thrust effect.
Control of the working medium depends upon the purpose of use, and as far as possible the relative movement between the two individual or the two types of guide members will be used for control purposes. The piston or pistons operating as free pistons are also suitable for controlling purposes.